Lyes Dekar

A cluster based mobility prediction scheme for ad hoc networks

The ad hoc networks are completely autonomous wireless networks where all the users are mobile. These networks do not work on any infrastructure and the mobiles communicate either directly or via other nodes of the network by establishing routes. These routes are prone to frequent ruptures because of nodes mobility. If the future movement of the mobile can be predicted in a precise way, the resources reservation can be made before be asked, which enables the network to provide a better QoS. In this aim, we propose a virtual dynamic topology, which on one hand, will organize the network as well as possible and decreases the impact of mobility, and on the other hand, is oriented user mobility prediction. Our prediction scheme uses the evidence theory of Dempster-Shafer in order to predict the future position of the mobile by basing itself on relevant criteria. These ones are related to mobility and network operation optimisation. The proposed scheme is flexible and can be extended to a general framework. To show the relevance of our scheme, we combine it with a routing protocol. Then, we implemented the prediction-oriented topology and the prediction scheme which performs on it. We implemented also a mobility prediction based routing protocol. Simulations are made according to a set of elaborate scenarios.

A distributed strict strong coloring algorithm for broadcast applications in ad hoc networks

A challenging research area in computer networks is ad hoc networks. These are defined to be spontaneous and totally autonomous networks. Many communication protocols (like routing, resources sharing, ...) use broadcasting mechanism to diffuse or gather information. A strict strong coloring of a graph G is a vertex proper coloring of G such that each vertex of G is adjacent to at least one non empty color class. In this paper, we give a novel broadcasting approach based on a distributed algorithm for strict strong coloring.

A graph b-coloring based method for composition-oriented web services classification

Web services aim to be the key of the Web development in the next years, by enabling the deployment, the sharing and the gathering of functionalities in a more simple and flexible way. The expectable growth of the number of Web services makes the need for automatic organization and discovery of Web services more important. In this paper, we propose a new classification based on Web services composition. The Web services that are often composed, are grouped together dynamically. Then, we give a graph based approach, that uses the b-coloring to partition these Web services into clusters and maintain them.

A Resource Discovery Scheme for Large Scale Ad Hoc Networks Using a Hypercube-Based Backbone

A critical challenge in designing ad hoc networks is resource discovery. In this paper, we propose a resource discovery scheme for large scale ad hoc networks, which uses a hypercubes-based backbone. Hypercubes are constructed in the different localities of the network by considering closely its physical topology constraints and the hypercube multi-paths property. The constructed hypercubes are then connected to form a backbone. ADHT (Distributed Hash Table) is processed on these hypercubes to lookup and register the resources. To avoid overloading the resource discovery system, we propose a flexible mechanism where the dimension of every hypercube can be adapted according to the load. The efficiency and the contribution of our scheme are evaluated through extensive simulation and by comparison with well known existing resource discovery approaches.

Distance-2 Self-stabilizing Algorithm for a b-Coloring of Graphs

A b-coloring of a graph G is a proper k -coloring of Gsuch that for each color i , 1 ≤ i ≤k , at least one vertex colored with i is adjacentto every color j , with 1 ≤ j ≠ i ≤ k . This kind of coloring is useful to decompose anysystem into communities, where each community contains a vertexadjacent to all the other communities. This kind of organizationcan provide improving in many fields, especially in the dataclustering. In this paper we propose a new self-stabilizingalgorithm for finding a b-coloring of arbitrary undirectedconnected graphs. Because the characteristics of the b-coloringproblem, the proposed self-stabilizing algorithm use a distance-2knowledge.

A Self-Stabilizing (Δ+ 1)- Edge-Coloring Algorithm of Arbitrary Graphs

Given a graph G = (V, E), an edge-coloring of G is a function from the set of edges E to colors {1, 2. .., k} such that any two adjacent edges are assigned different colors. In this paper, we propose a self-stabilizing edge-coloring algorithm in a polynomial number of moves. The protocol assumes the unfair central dæ mon and the coloring is a (Δ + 1)-edge-coloring of G, where delta is the maximum degree in G. To our knowledge, we give the first self-stabilizing edge-coloring algorithm using (Δ + 1) colors of arbitrary graphs.

A Self-Stabilizing Web Services Communities Management Scheme

Web services high availability becomes an important challenge these last years, especially for critical systems. Traditional solutions to achieve availability are mostly based on replication. Another more recent approach consists of using Web services communities. A community is a group of different Web services with similar functionalities. So, the high availability of a Web service is ensured by other web services from the same community. In this paper, we present a self-stabilizing community management scheme, which enables to construct and manage the communities in a peer-to-peer manner. Thus, there is neither need to define previously the functionalities to represent nor to use a master Web service to manage the community. Moreover, we use a set of criteria to decide if two Web services should belong to the same community or not.

An incremental distributed algorithm for a partial Grundy coloring of graphs

A coloring of a graph G=(V,E) is a partition of {V1,V2...Vk} of V into k independent sets called color classes. A vertex v∈Vi is called a Grundy vertex if it is adjacent to at least one vertex in color class Vj, for every j < i. In the partial Grundy coloring, every color class contains at least one Grundy vertex. Such a coloring gives a partitioning of the graph into clusters for which every cluster has a clusterhead (the Grundy vertex) adjacent to some other clusters. Such a decomposition is very interesting for large distributed systems and networks. In this paper, we propose a distributed algorithm to maintain the partial Grundy coloring of any graph G when an edge is added